Fix ember v6 deprecate-import-onerror-from-ember deprecation

Author: felixbuenemann

packages/ember-cli-fastboot/fastboot/initializers/error-handler.js

@@ -1,5 +1,5 @@
 /* eslint-disable prettier/prettier */
-import Ember from 'ember';
+import { getOnerror, setOnerror } from '@ember/-internals/error-handling';
 
 /**
  * Initializer to attach an `onError` hook to your app running in fastboot. It catches any run loop
@@ -10,12 +10,12 @@ export default {
   name: 'error-handler',
 
   initialize: function() {
-    if (!Ember.onerror) {
+    if (!getOnerror()) {
       // if no onerror handler is defined, define one for fastboot environments
-      Ember.onerror = function(err) {
+      setOnerror(function(err) {
         const errorMessage = `There was an error running your app in fastboot. More info about the error: \n ${err.stack || err}`;
         console.error(errorMessage);
-      }
+      });
     }
   }
 };

test-packages/test-scenarios/oneerror-per-visit-test.mjs

@@ -24,7 +24,7 @@ appScenarios
           });
         });`,
         'instance-initializers': {
-          'setup-onerror.js': `import Ember from 'ember';
+          'setup-onerror.js': `import { setOnerror } from '@ember/-internals/error-handling';
           export function initialize(owner) {
             let isFastBoot = typeof 'FastBoot' !== 'undefined';
             let fastbootRequestPath;
@@ -36,12 +36,12 @@ appScenarios
 
             console.log('setting up error handler ' + fastbootRequestPath);
 
-            Ember.onerror = function (error) {
+            setOnerror(function (error) {
               if (isFastBoot) {
                 error.fastbootRequestPath = fastbootRequestPath;
                 throw error;
               }
-            };
+            });
           }
 
           export default {
@@ -52,12 +52,15 @@ appScenarios
         routes: {
           'application.js': `import Route from '@ember/routing/route';
           import { action } from '@ember/object';
-          import Ember from 'ember';
+          import { getOnerror } from '@ember/-internals/error-handling';
 
           export default class ApplicationRoute extends Route {
             @action
             error(err) {
-              Ember.onerror(err);
+              const onerror = getOnerror();
+              if (onerror) {
+                onerror(err);
+              }
             }
           }
           `,